Project description:We recently developed an easy, efficient and scalable method for tagging and live cell imaging of non-repetitive, endogenous chromosome regions via CRISPR/Cas9 mediated knock-in of a TetO repeat. For this purpose, we created optimized and irregular 48-mer and 96-mer TetO repeats. Since it is known that repetitive regions in the human genome can induce H3K9me3-mediated heterochromatin formation, we tested whether 48-mer and/or 96-mer TetO repeats induce H3K9me3 flanking their insertion sites. Using a newly developed method called as CUT&RUN, we showed that there was no significant difference in the H3K9me3 pattern flanking the insertion sites of TetO repeats when compared to wild-type cells.
Project description:The antiviral protein MORC3 is frequently inhibited by viruses. To counteract viral antagonism, MORC3 represses a noncanonical pathway of type-I-interferon (IFN) such that viral inhibition of MORC3 triggers (>10,000-fold) IFN induction. How MORC3 represses this pathway, and why IFN induction upon MORC3 loss is so potent without canonical IRF3/7 transcription factors, is unknown. Here, we show that MORC3 restricts chromatin accessibility at tandem repeat elements harboring up to 61 homotypic transcription factor motifs. One such element becomes a potent enhancer of IFNB1 upon MORC3 loss. Its motif cluster contains 45 PU.1 binding sites and is necessary and sufficient for MORC3-mediated repression and enhancer activity upon MORC3 loss. PU.1 recruits MORC3 to repress this enhancer by recruiting DAXX and enabling H3.3 incorporation. Upon MORC3 loss, PU.1 drives IRF3/7-independent IFN induction. Other restricted tandem repeats contain homotypic motif clusters of SPI, AP-1, and SP/KLF transcription factors. Our findings uncover a TF motif cluster–driven repression mechanism by MORC3 at tandem repeats, enabling specific repression of an IFNB1 enhancer such that viral antagonism of MORC3 induces interferon.
Project description:Retroelement activation is emerging as a significant factor in the pathogenesis of neurodegenerative diseases. SINE-VNTR-Alu (SVAs) are hominid-specific retroelements that create genetic variation through insertion polymorphisms and variable short tandem repeat (STR) lengths. We investigate how the SVA (CCCTCT)n STR contributes to the striatal neurodegenerative disorder X-linked Dystonia Parkinsonism (XDP), where the repeat expansion length within the pathogenic SVA is inversely correlated with disease onset age. Phenotypic and transcriptomic analysis of XDP and isogenic SVA-deleted striatal organoids revealed that the SVA insertion drives hallmarks of neurodegeneration, including transcriptional dysregulation, decreased neuronal activity, and apoptosis, which are ameliorated by SVA deletion. We identify a (AGAGGG)n hexamer-containing RNA in the SVA that increases expression during organoid maturation and drives R-loop formation in organoids and XDP brain tissue. Knockdown of the (AGAGGG)n hexamer-containing RNA by antisense oligonucleotides rescues apoptosis in the XDP organoids. We demonstrate that a retrotransposon-derived tandem repeat RNA could cause neurodegeneration.
Project description:CD209L is a membrane glycoprotein with known glycan-binding properties and it also contains 2 N-glycosylation sequons at sites N92 and N361. Treatment with PNGase F in the presence of H218O, which removes N-linked glycans and isotopically labels the formerly-glycosylated site, confirmed that both unmodified and formerly-glycosylated versions of the peptide spanning the N92 N-glycosylated sequon were present. This suggests that a portion of CD209L protein is N-glycosylated at site N92. nUPLC-MS/MS analyses of CD209L digests enabled detection of a glycopeptide consistent with high-mannose type N-linked glycosylation.